I want to add a personal PSA, because I was at a supermarket when encountered someone "avoiding" the "higher dose" vit D3 of 5000 IU because they heard it could be "toxic" and they could overdose. Yes, Vitamin D, like A, E & K, can be stored in fat. But its very ,very hard to OD unless you are chugging liquid D. As a sufferer of autoimmune disorder (also linked to low Vit D), I'm going to tell you it really is safe to up those doses (those who spends lots of time outdoors may not have as much of an issue, but could still benefit from some supplementation). I did a trial of taking 10,000 IU every other day (basically 60,000 a week) for a month before my level was checked. My level came back at 73 = perfect.